Re: weird macro params issue

Friday, May 23, 2008, 11:47:08 AM, Denis wrote:

> I followed the discussion without commenting because I am not really a
> user of Freemarker. However Felix, who is a user, as I understand  
> would be comfortable with the Freemarker 2.4 solution presented by  
> Jonathan.
>
> If you still do decide to implement the feature, make it well  
> documented and put it on the front page,

No... It's a quite subtle detail, there is no much point bragging
about it.

> in comparisons and shoot outs. Make it a differentiator for
> Freemarker.
>
> Some people will protest, that are used to defaults as mere constant  
> values,

Puzzling opinion... why would anyone *protest* about it? Yeah, I can
see as someone finds <#macro chapter title linkLabel=title> and
"WHAT??? This Is Outrageous!!! Defaults were always constants! This is
how our fathers did it, and the fathers of our fathers!". ;)

> but it will give one more reason to use Freemarker as opposed to
> other template engines for those who see the value.
>
> On 22 mai 08, at 14:48, Jonathan Revusky <[email protected]> wrote:
>
>> On Thu, May 22, 2008 at 3:28 PM, Attila Szegedi <[email protected]>  
>> wrote:
>>> On 2008.05.22., at 15:10, Tim Diggins wrote:
>>>
>>>> I hope you're not arguing that character count is more important  
>>>> than
>>>> understandability / readability / learnability.
>>>
>>> I'm not. As a matter of fact, to this day I prefer the old existence
>>> built-ins "?default" and "?exists" for similar reasons I prefer Java
>>> "extends" to C# ":" :-)
>>> I don't feel that <#macro m a b=a> impacts understandability or
>>> readability. To me,
>>>
>>> <#macro a b!>
>>>  <#if !b??>
>>>    <#local b=a/>
>>>  </#if>
>>> </#macro>
>>>
>>> would, honestly, be less understandable IMHO. The b=a doesn't
>>> introduce any new syntax - it's your good ol' defaulted argument, the
>>> only novelty is it's defaulting to value of another argument, which  
>>> is
>>> also visually located near it, so I don't believe it makes
>>> understanding the meaning too daunting.
>>
>> Actually, I just realized something.
>>
>> Independently of whether we support this particular thing, our
>> semantics are quite different from Python semantics. In python, the
>> example I gave that failed:
>>
>> def foo(x, y=x) :
>>
>> Basically it fails because the default values in python are values.
>> They must be constant values that can be calculated when you define
>> the function.
>>
>> FreeMarker default values (in 2.4 also) are not actually values, they
>> are expressions. (Of course, an expression that evaluates to a
>> constant value is very often used.)
>>
>> So I guess the "what would Guido do" argument is kind of weak because
>> we're already so far away. It would seem then that if the default
>> values in a macro definition can be expressions (later evaluated on
>> invocation) that this use case is consistent with that.
>>
>> So I guess my view is shifting on this. I honestly had the distinct
>> impression that you were implementing this basically because it could
>> be done, which of course made me nervous. The whole multipass thing
>> for tricky cases might be unnecessary, and it might be better just to
>> scan straightforwardly left to right as Felix suggested. Though, if
>> you are implementing it, you can do it as you want as far as I'm
>> concerned.
>>
>> JR
>>
>>>
>>> Attila.
>>>
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-- 
Best regards,
 Daniel Dekany


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